1. Field of the Invention
The present invention relates to a semiconductor processing. More particularly, the invention relates to reflectivity measurement and deposited films in situ or online.
2. Background of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers are deposited and etched from substrates in order to form features on the substrate. One important aspect of forming electronic features is photolithography. Photolithography is the patterning of the layers formed on the substrate for removal using an etching process. In a photolithography process, a material such as a photoresist is deposited on the top surface of the layers formed on the substrate and is then patterned by exposing portions of the photoresist to a light source. The exposed portions of the photoresist are determined by a mask which is patterned to define the features which are desired on the substrate. Depending on whether the photoresist is a positive or negative photoresist, either the exposed portion of photoresist or the unexposed portion of photoresist is removed by reacting the photoresist with one or more chemicals. The etching process then selectively etches the under-layers exposed through the remaining photoresist material.
As features sizes decrease, patterning lines and other features on substrates has become increasingly important and difficult. In particular, the effect of the under-layers in scattering the light used to cure the photoresist should be avoided. Otherwise, the patterning of the photoresist will be less than desired. As a result, anti-reflective coatings (ARC) such as dielectric anti-reflective coatings (DARC) are typically employed to ensure that the light used to expose the photoresist in the photography process is not scattered but rather absorbed.
Deposition techniques are currently known in the art which can deposit conventional dielectric ARC materials. However, over time, processes can vary, resulting in the inability of the dielectric ARC materials to achieve the desired reflectivity. Accordingly, the reflectivity of the dielectric ARC materials is periodically measured during processing. Reflectivity can typically be determined by the thickness as well as the quality of the deposition formed on the substrate.
In order to ensure that the dielectric ARC material is adequate to support the application in which it is used, the wafers are periodically moved to a stand-alone chamber where the reflectivity of the film can be measured using conventional optical techniques. While this conventional methodology is useful to determine whether or not the process is adequate on the particular wafer undergoing inspection, moving substrates to separate chambers for measurement is expensive and time-consuming.
Therefore, there is a need for a method and apparatus for determining the reflectivity of arc materials, anti-reflective coating materials in situ or on-line.
The invention generally provides an apparatus and method for measuring the reflectivity of an object.
One aspect of the invention provides an apparatus comprising a vacuum chamber comprising an aperture for transfer of the object therethrough and an opening for transmitting an optical signal from a region external to the vacuum chamber into an internal region of the chamber. A transmitting assembly including a light source is positioned external to the vacuum chamber and proximate the opening to transmit an optical beam into the internal region. The apparatus further comprises a receiving assembly adapted to receive a reflected portion of the optical beam and a signal processing system coupled to the receiving assembly. The signal processing system is programmed to determine the reflectivity of a surface of a substrate disposed in the vacuum chamber.
Another aspect of the invention provides an apparatus comprising a vacuum chamber body defining an aperture for transfer of the object therethrough, a showerhead disposed on the vacuum chamber body, a substrate support member disposed in the vacuum chamber body, a transmitting assembly and a receiving assembly. The transmitting assembly comprises a light source positioned in a region external to the vacuum chamber body and one or more transmitting cables having a light input end disposed proximate the light source and a light output end adapted to deliver an optical beam into an internal region of the vacuum chamber body. At least a portion of the transmitting cable is disposed in the showerhead. At least a portion of the receiving assembly is disposed in the internal region and is adapted to receive a reflected portion of the optical beam.
Another aspect of the invention provides a method for measuring reflectivity of a substrate disposed in a vacuum processing chamber comprising a gas showerhead at one end of the chamber. The method comprises delivering an optical beam through the showerhead and onto a surface of the substrate and receiving reflected portions of the optical beam at a signal receiving assembly. In one embodiment, the step of delivering comprises emitting the optical beam onto a surface of the showerhead, wherein the optical beam is reflected from the surface of the showerhead onto the surface of the substrate.
Another aspect of the invention provides a method for measuring reflectivity of a substrate disposed in a vacuum processing chamber gas having a showerhead at one end of the chamber. The method comprises delivering an optical beam from a region lateral of the substrate and onto a surface of the showerhead, wherein the optical beam is reflected from the surface of the showerhead onto the surface of the substrate. Reflected portions of the optical beam are received at a signal receiving assembly.